This invention relates to dispensing ink at intervals selected to correspond to the amount of ink that is forced through a silk screen during a period of operation by a squeegee for printing. More particularly, the present invention relates to a system and method capable of automatic operation to dispense a predetermined quantity of ink that may comprise thermoplastic paint maintained in a liquid state in a reservoir through a conduit in response to a control signal generated by counting up a predetermined number of pulses corresponding to operations of a squeegee used to pass through a silk screen for printing operations.
It is common practice to mark objects, particularly containers such as bottles, by a silk-screen printing process wherein a screen made of silk or wire mesh has its surface rendered non-porous to ink or paint except in those areas which delineate the marking. The ink can pass through the porous areas of the screen onto any surface in contact with the screen. A frame is used to hold the screen so that a squeegee pressed against one surface of the screen will force ink through the porous areas as the squeegee is moved along the screen for each printing operation. For a printing operation, it is known in the art to use solvent-based ink or thermoplastic paint which is maintained in a liquid state by resistively heating steel-wire gauze used to form the silk screen. The thermoplastic paint is manually fed in solid form onto the heated surface of the screen where it is liquefied before printing. There is a need, however, to dispense ink or paint to the silk screen in such a manner that a sufficient quantity of ink or paint is always present for printing operations. Hand feeding paint or manual control of the flow of ink or paint to the silk screen requires careful monitoring by an operator to avoid depletion of the paint in the screen or overfilling the ink supply. It is not acceptable, for example, to dispense ink at a given flow rate or at predetermined intervals of time since the printing operation may be carried out on an intermittent or irregular time basis.